In presently-used telecommunications systems, power is supplied using the technique shown in FIG. 1. An on-line rectifier 11 is powered by the low-voltage mains 12 or by an electricity generator set 13. The rectifier delivers a DC voltage, e.g. 48 volts, to the telecommunications equipment 14.sub.1 to 14.sub.3.
Depending on the needs of the equipment, the following are provided:
a DC-to-DC converter 15.sub.1 delivering DC voltages of 5 volts and 12 volts, for example; PA1 a booster 15.sub.2 delivering a DC voltage of 54 volts, for example; and PA1 a ringing inverter 15.sub.3, delivering an AC voltage of 80 volts, for example. PA1 an AC-to-DC converter 21; PA1 an energy storage device 22; and PA1 a DC-to-AC converter 23. PA1 the equipment to be implemented; PA1 the electrical conductors used; and/or PA1 electricity consumption. PA1 an AC main power supply used under normal conditions; PA1 an energy storage unit used as a DC secondary electrical power supply under back-up conditions; and PA1 means for detecting failure of said main power supply, and for then switching over to a back-up mode; PA1 directly by said main power supply under normal conditions; PA1 directly by said secondary power supply under back-up conditions.
If computer peripherals 16 are present that require an AC voltage (e.g. 230 V), an inverter 17 is used.
Finally, one or more batteries 18, charged by the energy delivered by the rectifier 11, automatically take over from the power supply in the event of a problem.
That technique suffers from numerous drawbacks. In particular, it assumes the use of a high-power rectifier which gives rise to considerable dissipation, as appears more clearly on reading Table I.
In addition, the means required are costly and voluminous. Finally, that technique requires electrical cables of large section to be used.
Uninterruptible power supplies (UPSs) for delivering AC are also known that are used for AC-powered equipment such as computer equipment.
Two types of architecture are used for UPSs, shown respectively in FIGS. 2A and 2B, namely on-line architecture (FIG. 2A), and off-line architecture (FIG. 2B).
Each of the power supplies comprises:
The drawback with those techniques is that they need an inverter 23 that is capable of delivering the entire power requirement of all of the items of equipment 25.sub.1 to 25.sub.N that are to be powered. Such an inverter 23 constitutes the most costly part of the UPS.
In addition, those techniques require the use of electrical cables that are of large section.
In the off-line power supply, a changeover switch 24 makes it possible to switch over from the main power supply to the back-up power supply.
In contrast, in the on-line power supply, the electrical energy received from the mains 12 or from an electricity generator set 13 always passes through both converters 21 and 23, which naturally gives rise to considerable losses. In addition, that technique requires a first AC-to-DC conversion stage 21 that operates at full power.